This invention relates generally to diagnostic equipment and service of fuel delivery units such as conventional solenoid-operated fuel injectors of the type commonly used in internal combustion engines and diesel engines, and in land, marine and other applications. More specifically, the invention relates to apparatus and methods for cleaning and testing the performance of such fuel injectors.
Fuel injectors of this type include a relatively small flow passage and a small in-line poppet valve that is pulsed open and closed at high frequency by an integral solenoid coil to provide fuel flow to the engine. Several known abnormal conditions in these components result in inefficient engine performance.
Fuel contaminants passing through the fuel filter may build-up in the passage of an injector and restrict fuel flow from that injector. Entrapment of such contaminants in the poppet valve may prevent the valve from fully closing, resulting in excess fuel flow. And electrical failure of the solenoid results in an inoperative injector, and again no fuel delivery from that injector. Each of these conditions may result in inefficient engine performance, from, among other things, an improper fuel-air interpretation and compensation in the engine.
Numerous prior devices have been utilized for checking the flow rate through fuel injectors and cleaning the injectors by flowing a cleaning agent therethrough in normal and sometimes reverse direction. One prior method for testing flow rate includes placing the injector into a device adapted to capture the output flow in a graduated cylinder. The flow rate is then determined by the volume of fluid collected in the cylinder over a measured period of time. See e.g., Bunch, U.S. Pat. No. 5,000,043. The method of flow measurement utilized in Hart et al., U.S. Pat. No. 5,020,326 includes taking pressure readings with a "standard" fuel injector and then comparing those pressure readings (or calculations therefrom) with data collected from injectors in the automobile. Hartopp, U.S. Pat. No. 4,804,005 discloses a device with a conventional mechanical flow meter that may be switched into and out of an injector fluid flow circuit for measuring the flow rate. The prior art also teaches apparatus and methods for verifying that the spray angle from an injector appears correct. See e.g., Griggs, U.S. Pat. No. 5,571,959. Unfortunately, these prior methods and devices for checking and cleaning fuel injectors are labor intensive, and require the vigilant observation and participation of a trained technician to obtain reasonably accurate and repeatable results.
In addition, verifying that the resistance of the solenoid coil is within pre-defined limits, and that the coil is functioning properly, is typically accomplished via conventional electrical testing on individual injectors, again requiring the active participation of the service technician.